Water heater with anti-deformation skin

ABSTRACT

A water heater including a tank to hold water to be heated, the tank having an outer surface, and a source of heat for heating the water in the tank. The water heater further includes a jacket surrounding the tank, the jacket having an inner surface facing the tank, a plastic skin attached to the outer surface of the tank, and an annular space between the tank and the jacket. In addition, the water heater includes foam insulation within the annular space. The foam insulation cures to form a porous solid layer of insulation between the tank and jacket, and the foam insulation shrinks during curing. The foam insulation adheres to the inner surface of the jacket, and the foam insulation does not adhere to the plastic skin during curing, to thereby reduce a deforming load on a portion of the jacket opposite the plastic skin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/083,792, filed on Nov. 24, 2014, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present invention relates to a water heater, and more specifically a water heater with insulation between an inner tank and outer jacket.

Positioning insulation between an inner tank and outer jacket is a common practice in the field of water heaters, and is similar to practices used in other various appliances (e.g., refrigerators). In the case of water heaters, the insulation is adhered to both the inner tank and the outer jacket to insulate the inner tank. A common, industry-wide problem occurs when the insulation positioned between the inner tank and the outer jacket shrinks due to varying ambient temperatures and/or during the cure cycle. For example, the insulation shrinks in cold ambient temperatures, and as the insulation contracts a deforming load is applied to the both the inner tank and outer jacket since the insulation is adhered to both. Most commonly, the outer jacket is the weaker of the two components, and the outer jacket is deformed by the contracting insulation.

One previously presented solution has been to position the insulation in a bag surrounding the inner tank, eliminating any adhesion between the insulation and the tank or jacket. However, positioning the insulation in a bag presents additional manufacturing complications and the bag's permeability results in lowered water heater efficiencies.

An additional solution to shrinking insulation is presented in U.S. Pat. No. 3,940,195 (“the '195 Patent”) describing a refrigeration cabinet 10 with an outer shell 11 and an inner liner 12 creating a space 14 therebetween receiving rigid cast resin foam insulation 15. The '195 Patent describes the tendency for the expansion and contraction of the insulation 15. Such expansion and contraction, particularly at the projections 19, can cause stress and damage in the liner 12. The '195 Patent proposes applying a sheet 21 over the projections 19 to provide a cushion spaced that permits relative movement between the liner 12 and the insulation 15 around the projections 19. In other words, the sheet 21 prevents the insulation from closely embracing the projections 19, thereby reducing fractions of the liner 12 under thermal stress. In the '195 Patent, the sheet 21 is applied directly over the projections 19 to prevent the insulation 15 from adhering thereto. The teachings of the '195 Patent are limited to preventing the insulation 15 from adhering to two surfaces at right angles to one another.

SUMMARY

In one embodiment, the invention provides a water heater including a tank to hold water to be heated, the tank having an outer surface, and a source of heat for heating the water in the tank. The water heater further includes a jacket surrounding the tank, the jacket having an inner surface facing the tank, a plastic skin attached to the outer surface of the tank, and an annular space between the tank and the jacket. In addition, the water heater includes foam insulation within the annular space. The foam insulation cures to form a porous solid layer of insulation between the tank and jacket, and the foam insulation shrinks during curing. The foam insulation adheres to the inner surface of the jacket, and the foam insulation does not adhere to the plastic skin during curing, to thereby reduce a deforming load on a portion of the jacket opposite the plastic skin.

In another embodiment the invention provides a method of assembling a water heater having a tank and a jacket including positioning the jacket around the tank to define an annular space therebetween, and adhering a plastic skin to a selected portion of the outer surface of the tank facing the jacket. The method further includes introducing foam insulation into the annular space, shrinking the foam insulation in response to a reduction in ambient temperature, and adhering the foam insulation to the inner surface of the jacket and the outer surface of the tank except the selected portion of the outer surface of the tank due to the foam not adhering to the plastic skin. In addition, the method includes preventing the shrinking foam from applying a deforming load to a portion of the jacket that is opposite to the selected portion of the outer surface of the tank.

In another embodiment the invention provides a method of assembling first and second components including positioning the second component around the first component to define an annular space therebetween, adhering a plastic skin to an outer surface of the first component facing the second component, and introducing foam insulation into the annular space. The foam insulation adhering to the first and second components, but not adhering to the plastic skin. The method further includes shrinking the foam insulation in response to a reduction in ambient temperature, and separating the foam insulation from the plastic skin in response to shrinking of the foam insulation to prevent the shrinking foam from applying a deforming load to a portion of the second component that is opposite to the plastic skin attached to the first component.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial exploded view of a water heater tank and anti-deformation barriers.

FIG. 2 is an enlarged partial view of the water heater tank and anti-deformation barriers of FIG. 1.

FIG. 3A is a cross-sectional schematic view of a water heater with a foam insulation in a first, expanded state.

FIG. 3B is a cross-sectional schematic view of the water heater of FIG. 3A with the foam insulation in a second, shrunken state.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

With reference to FIG. 1, a water heater 10 is illustrated with portions not illustrated for clarity purposes. More specifically, the water heater 10 includes a tank 14 to hold water to be heater, and the tank 14 includes an outer surface 18. The water heater 10 further includes a source of heat (e.g., electrical elements, condenser coil, burner, etc.) for heating the water in the tank 14. In the illustrated embodiment, the water heater 10 is an electrical water heater with electrical heating elements positioned within the tank 14. The electrical heating element are electrically connected via fittings 22 that extend through the tank 14. A jacket 26 (not illustrated in FIGS. 1-2, but schematically shown in FIGS. 3A-3B) surrounds the tank 14, and the jacket 26 includes an inner surface 30 facing the tank 14. The jacket 26 is coaxially positioned around the tank 14 and an annular space 34 is created between the tank 14 and the jacket 26. The assembled water heater 10 further includes foam insulation 38 positioned within the annular space 34.

The jacket 26 is most commonly thinner and/or a weaker structure than the tank 14. It is common for the jacket 26 to also include a stress-enhancing feature 42 (i.e., a weakening feature). The stress-enhancing feature 42 may be, for example, a hole in the jacket 26 to accommodate a feature of the water heater 10. The stress-enhancing features 42 make the jacket 26 prone to deformation in the region of the stress-enhancing feature in response to a deforming load (e.g., shrinking foam insulation, as discussed in detail below). The water heater 10 further includes an anti-deformation barrier (i.e., a plastic skin 46, 50) attached to the outer surface 18 of the tank 14. More specifically, the plastic skins 46, 50 are attached to the outer surface 18 of the tank 14 opposite the stress-enhancing features 42 on the jacket 26, for reasons described in detail below. The portions of the tank opposite the stress-enhancing features 42 of the jacket 26 may be referred to as “stress-relieving portions” of the tank.

The plastic skins 46, 50 do not allow foam insulation to adhere thereto. The plastic skins 46, 50 may be made out of an adhesive tape (e.g., 3M Polyethylene Protective Tape 4179, 2 mm light gauge tape, etc.) or any other suitable material that would adhere to the tank 14, but would not adhere to the foam insulation 38 or permit the foam insulation 38 to adhere to it. In the illustrated embodiment, the plastic skin 46 is approximately eight inches in a width dimension 54 and between approximately twelve to twenty-four inches in a length dimension 58. Correspondingly, the plastic skin 50 is approximately eight inches in a width dimension 62 and between approximately three to six inches in a length dimension 66. In the illustrated embodiment, the plastic skin 46 is positioned between the electrical fittings 22, and the plastic skin 50 is positioned above the electric fittings 22 overlapping a portion of a head 70 of the tank 14.

With reference to FIG. 2, the jacket 26 and its stress-enhancing features are configured to avoid alignment with certain features of the tank 14, such that the stress-relieving portions of the tank 14 can more easily receive the plastic skins 46, 50. As a result, the plastic skin 50 does not overlap any portion of a thermostat 74, but the plastic skin 50 may overlap a spud 78. The plastic skin 50 overlaps the spud 78 typically only if there is no thread interference. In alternative embodiments, any number of plastic skins, having various size dimensions or shapes, may be positioned anywhere on the outer surface 18 of the tank 14. In one alternative embodiment, a plastic skin strip extends around the entire circumference of the tank. The plastic skins, however, do not cover the entirety of the outer surface 18 of the tank 14. In other words, there is a portion of the outer surface 18 not covered by the plastic skins.

With reference to FIGS. 3A-3B, the arrangement of water heater 10 components is schematically shown with dimensional characteristics exaggerated for clarify purposes. The plastic skin 46, 50 is adhered to the outer surface 18 of the tank 14 over the stress-relieving portions of the tank 14 for the particular jacket 26 that will be installed on the tank 14. The jacket 26 is positioned around the tank 14, and then the foam insulation 38 is introduced into the annular space 34. The foam insulation 38 adheres to the tank 14 and the jacket 26, and the foam insulation 38 cures to form a porous solid layer of insulation between the tank 14 and jacket 26. However, the foam insulation 38 does not adhere to the plastic skin 46, 50. In other words, the foam insulation 38 adheres to the inner surface 30 of the jacket 26 and the outer surface 18 of the tank 14, but not to the plastic skin 46, 50. A known problem of foam insulation 38, as previously described, is that the foam insulation 38 shrinks during curing and/or in response to a reduction in ambient temperature. This foam shrinkage can create a deforming load on the structure(s) to which the foam is adhered to.

In the illustrated embodiment, as the foam insulation 38 shrinks, the foam insulation 38 remains adhered to the inner surface 30 of the jacket 26 and the outer surface 18 of the tank 14, but does not adhere to the plastic skin 46, 50 to thereby reduce a deforming load on the jacket 26 opposite the plastic skin 46, 50. More specifically, the foam insulation 38 does not adhere to the plastic skin 46, 50 to thereby reduce a deforming load on a portion of the jacket 26 that includes the stress-enhancing feature 42 opposite the plastic skin 46, 50. In other words, the plastic skins 46, 50 are strategically positioned on the outer surface 18 of the tank 14 opposite the selected portions of the jacket 26 that include the stress-enhancing features 42 to reduce the deforming load of the shrinking foam on the jacket 26.

There are several reasons that the plastic skin 46, 50 on the outer surface 18 of the tank 14 are positioned opposite the stress-enhancing features 42 on the jacket 26, including facilitation of assembly (i.e., to accurately position the plastic skin 46, 50 on the tank 14). In addition, it is advantageous to position the plastic skin 46, 50 on the tank 14 because when the foam insulation 38 shrinks and pulls away from the plastic skin 46, 50, the foam insulation 38 will remain adhered to the surrounding outer surface 18 of the tank 14 resulting in a void of trapped air 82 (FIG. 3B) adjacent the plastic skin 46, 50 and tank 14. The void of trapped air 82 continues to provide beneficial insulation for the water heater 10.

In alternative embodiments, the plastic skins may initially have a low adhesion with the foam insulation such that the plastic skin and foam insulation are initially adhered to one another, but the adhesion between the plastic skin and foam insulation would break under a load that is below the load required to deform the jacket. In other words, before the deforming load from the shrinking foam insulation is large enough to deform the jacket, the adhesive bond between the plastic skin and the foam insulation would break allowing the plastic skin and foam insulation to separate. In this manner, prevention of adhesion between the plastic skin and foam insulation at all times is not required.

Various features and advantages of the invention are set forth in the following claims. 

What is claimed is:
 1. A water heater comprising: a tank to hold water to be heated, the tank having an outer surface; a source of heat for heating the water in the tank; a jacket surrounding the tank, the jacket having an inner surface facing the tank; a plastic skin attached to the outer surface of the tank; an annular space between the tank and the jacket; and foam insulation within the annular space, the foam insulation curing to form a porous solid layer of insulation between the tank and jacket; wherein the foam insulation shrinks during curing; wherein the foam insulation adheres to the inner surface of the jacket; wherein the foam insulation does not adhere to the plastic skin during curing, to thereby reduce a deforming load on a portion of the jacket opposite the plastic skin.
 2. The water heater of claim 1, wherein: the jacket includes a stress-enhancing feature; and the plastic skin is applied to a portion of the tank opposite the stress-enhancing feature, but not to another portion of the tank, such that the foam insulation adheres to the outer surface of the tank except where the plastic skin is applied.
 3. The water heater of claim 2, wherein the stress-enhancing feature includes a hole in the jacket.
 4. The water heater of claim 1, wherein the source of heat for heating the water is an electrical heating element positioned within the tank.
 5. A method of assembling a water heater having a tank and a jacket, the method comprising: positioning the jacket around the tank to define an annular space therebetween; adhering a plastic skin to a selected portion of the outer surface of the tank facing the jacket; introducing foam insulation into the annular space; shrinking the foam insulation in response to a reduction in ambient temperature; adhering the foam insulation to the inner surface of the jacket and the outer surface of the tank except the selected portion of the outer surface of the tank due to the foam not adhering to the plastic skin; and preventing the shrinking foam from applying a deforming load to a portion of the jacket that is opposite to the selected portion of the outer surface of the tank.
 6. The method of claim 5, wherein the jacket includes a stress-enhancing feature; and wherein the selected portion of the outer surface of the tank is opposite the stress-enhancing feature.
 7. A method of assembling first and second components, the method comprising: positioning the second component around the first component to define an annular space therebetween; adhering a plastic skin to an outer surface of the first component facing the second component; introducing foam insulation into the annular space, the foam insulation adhering to the first and second components, but not adhering to the plastic skin; shrinking the foam insulation in response to a reduction in ambient temperature; and separating the foam insulation from the plastic skin in response to shrinking of the foam insulation to prevent the shrinking foam from applying a deforming load to a portion of the second component that is opposite to the plastic skin attached to the first component.
 8. The method of claim 7, wherein adhering a plastic skin includes adhering tape to the outer surface of the first component.
 9. The method of claim 7, wherein the second component includes weakening features making the second component prone to deformation in response to a deforming load; and wherein adhering a plastic skin includes adhering the plastic skin on the first component opposite the weakening features.
 10. The method of claim 7, wherein separating the foam insulation from the plastic skin creates a void of trapped air adjacent the first component.
 11. The method of claim 7, wherein the first component is a water heater tank and the second component is a water heater jacket. 